Clinical outcomes of high-flow nasal cannula in COVID-19 associated postextubation respiratory failure. A single-centre case series

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Clinical outcomes of high-flow nasal cannula in COVID-19 associated postextubation respiratory failure.

A single-centre case series

Francesca Simioli, Anna Annunziata, Gerardo Langella, Giorgio E. Polistina, Maria Martino, Giuseppe Fiorentino

Department of Respiratory Pathophysiology, Monaldi-Cotugno Hospital, Naples, Italy

PRACE ORYGINALNE I KLINICZNE

High flow nasal cannula (HFNC) is an alterna

tive device for oxygenation, which improves gas exchange and reduces the work of breathing [1].

In patients with acute respiratory failure of various origins, HFNC shows better comfort and oxygena

tion than standard oxygen therapy delivered through a face mask [2].

Postextubation respiratory failure is common and causes increased morbidity and mortality.

The reintubation rate is very variable but may reach 20% or more [3]. It has been related to respiratory mechanics, airway patency, and protection. In fact, adequate cough strength, minimal secretions, and alertness are necessary for successful extubation [4].

Moreover, a randomised controlled trial has shown a significant reduction in the reintubation rate for

Anestezjologia Intensywna Terapia 2020; 52, 5: 377–380 Otrzymano: 12.06.2020, zaakceptowano: 26.07.2020

patients treated with HFNC as compared with stan

dard oxygen [5]. In another largescale trial, HFNC was equivalent to NIV in patients at high risk of extu

bation failure [6]. Even if the ideal treatment for pre

vention of reintubation has yet to be determined for highrisk patients, HFNC may be considered as a ref

erence therapy during the postextubation period [7].

HFNC has been widely employed during the COVID19 pandemic [8, 9]. However, no data have been published about postventilation manage

ment. Furthermore, weaning failure prediction tools, such as ROX index, have not been validated yet for COVID19.

The purpose of this paper is to report a single

centre experience on the effectiveness and safety of HFNC in the weaning of COVID19 patients.

ADRES DO KORESPONDENCJI:

Francesca Simioli, Department of Respiratory Pathophysiology, Monaldi-Cotugno Hospital, Naples, Italy, e-mail: francesimioli@gmail.com

Abstract

Background: A high-flow nasal cannula (HFNC) is an alternative device for oxygena- tion, which improves gas exchange and reduces the work of breathing. Postextubation respiratory failure causes increased morbidity and mortality. HFNC has been widely employed during the COVID-19 pandemic. The purpose of this paper is to report a single- centre experience on the effectiveness and safety of HFNC in weaning COVID-19 patients.

Methods: Nine patients showed severe acute respiratory failure and interstitial pneu- monia due to SARS-CoV-2. After mechanical ventilation (5 Helmet CPAP, 4 invasive mechanical ventilation), they were de-escalated to HFNC. Settings were: 34–37°C, flow from 50 to 60 L min^-1. FiO₂ was set to achieve appropriate SpO₂.

Results: Nine patients (4 females; age 63 ± 13.27 years; BMI 27.2 ± 4.27) showed a base- line PaO₂/FiO₂ of 109 ± 45 mm Hg. After a long course of ventilation all patients improved (PaO₂/FiO₂ 336 ± 72 mm Hg). Immediately after initiation of HFNC (2 hours), PaO₂/FiO₂ was 254 ± 69.3 mm Hg. Mean ROX index at two hours was 11.17 (range:

7.38–14.4). It was consistent with low risk of HFNC failure. No difference was observed on lactate. After 48 hours of HFNC oxygen therapy (day 3), mean PaO₂/FiO₂ increased to 396 ± 83.5 mm Hg. All patients recovered from respiratory failure after 7 ± 4.1 days.

Conclusions: HFNC might be helpful in weaning COVID-19 respiratory failure. Effec- tiveness and comfort should be assessed between 2 and 48 hours. Clinical outcomes, oxygenation, and ROX index should be considered, to rule out the need for intubation.

Further evidence is required for firm conclusions.

Key words: ventilation, weaning, COVID19, highflow nasal cannula, postextuba

tion respiratory failure, ROX index.

Należy cytować anglojęzyczną wersję: Simioli F, Annunziata A, Langella G, Polistina GE, Martino M, Fiorentino G. Clinical outcomes of high-flow nasal cannula in COVID-19 associated postextubation respiratory failure. A single-centre case series. Anaesthesiol Intensive Ther 2020; 52, 5: 373–376.

doi: https://doi.org/10.5114/ait.2020.101007

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METHODS

This was a crosssectional, observational case series. The study was approved by the local Ethics Committee of University of Campania “Luigi Vanvi

telli” and A.O.R.N. Ospedali dei Colli in accordance with the 1976 Declaration of Helsinki and its later amendments. Written informed consent was ob

tained from all subjects. We retrospectively analy

sed patient records from the Subintensive Care Unit of Cotugno Hospital, Naples, Italy. Nine pa

tients were admitted for severe acute respiratory failure and interstitial pneumonia. SARSCoV2 was confirmed by realtime polymerase chain reaction (RTPCR) on nasopharyngeal swab. All patients showed a typical progressive stage at chest imag

ing. Pharmacological treatment was administered according to local guidelines as a rescue measure because no specific antiSARSCoV2 drugs were available (Table 1).

All patients underwent mechanical ventilation (5 Helmet CPAP, 4 invasive mechanical ventilation).

A substantial duration of ventilation (14 ± 3.5 days) was needed until improvement of gas exchange.

Weaning was initiated following a stable period of ventilation. Nevertheless, SpO₂ and pO₂ when wean

ing directly to standard oxygen therapy were unsa

tisfactory with dyspnoea and signs of respiratory fatigue. Considering age, comorbidities, spontane

ous breathing trial failure, and prolonged mechani

cal ventilation, we assumed that our patients were at highrisk of intubation.

We implemented a switch to HFNC set at 34–

37°C and a flow ranging from 50–60 L min¹. Tem

perature and flow were set considering the patient’s comfort [10, 11]. Delivered FiO₂ was set to achieve a target of SpO₂ ≥ 95% (93% in the case of pre

existing COPD). Blood gases were performed daily, as well as assessment of dyspnoea, respiratory rate, heart rate, blood pressure, oxygen saturation, and patient comfort. The ROX index is the ratio of oxy

gen saturation/FiO₂ to respiratory rate [12]. It is cur

rently used to evaluate HFNC efficacy on avoiding ventilation in patients with acute respiratory failure and pneumonia. A ROX index less than 2.85 at two hours is a predictor of HFNC failure. In our protocol, ROX index was calculated at two hours to assess HFNC failure promptly.

All patients were persistently positive for SARS

CoV2 at the time of HFNC initiation, as assessed by RTPCR. During the protocol the patients stayed in single isolation rooms.

Categorical data were expressed as number and percentage, whilst continuous variables as mean and standard deviation (SD). Differences before and after HFNC treatment were tested, according to the normal distribution, by the parametric paired Stu

dent’s ttest. A Pvalue < 0.05 was considered statis

tically significant.

TABLE 1. Patients outcomes

Patient 1 2 3 4 5 6 7 8 9

Gender F F F M F M M M M

Age (years) 65 62 66 47 36 74 75 72 71

BMI (kg m^-2) 34 28 23 25 34 28 24 23 26

Comorbidities Allergic

rhinitis – 2DM,

HTN HCM – COPD,

HTN HTN,

glaucoma COPD,

HTN, AF 2DM, HTN, CAD, VCD

Baseline P/F (mm Hg) 103 164 80 71 200 66 100 126 80

P/F on ventilation (mm Hg) 408 422 290 390 313 212 367 258 368

Lactate on ventilation

(mmol L^-1) 0.7 2.2 1.5 1.3 0.8 0.8 1.5 1.3 1.3

P/F on HFNC at 2 h (mm Hg) 218 322 245 166 325 145 340 252 273

Lactate on HFNC at 2 h (mmol L^-1)

0.9 1.9 3 2.2 2.2 0.8 1.9 0.7 1.9

ROX on HFNC at 2 h 13.19 12.47 7.38 9.98 12.37 10.57 10.25 9.9 14.4

HFNC temperature (°C) 34 34 34 34 34 37 37 37 37

HFNC flow (L min^-1) 60 60 60 55 55 50 50 60 50

P/F on HFNC at 48 h (mm Hg) 330 446 481 250 435 330 436 357 503

Lactate on HFNC at 48 h (mmol L^-1)

0.8 1.6 2.2 1.9 0.9 1.1 1.9 0.7 1

Therapy AZY, Hxc,

LMWH AZY, Hxc,

LMWH, L/R AZY, Hxc,

LMWH, L/R AZY, Hxc, LMWH AZY, Hxc,

LMWH AZY, Hxc,

LMWH, D/C, TOCI AZY, Hxc,

LMWH, L/R AZY, Hxc, LMWH,

D/C, TOCI AZY, Hxc, LMWH, D/C

DM – type 2 diabetes mellitus, HTN – systemic blood hypertension, HCM – hypertrophic cardiomyopathy, AF – atrial fibrillation, CAD – coronary artery disease, VCD – vascular cerebral disease, P/F – PaO₂/FiO₂, HFNC – high flow nasal cannula, AZY – azithromycin, Hxc – hydroxychloroquine, LMWH – low-molecular-weight heparin, L/R – lopinavir/ritonavir, D/C – darunavir/cobicistat, TOCI – tocilizumab

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379 High flow nasal cannula in COVID-19 post-ventilation management

RESULTS

Nine patients (4 females; age 63 ± 13.27 years;

BMI 27.2 ± 4.27 kg m²) showed ARDS and needed ventilation. Frequent comorbidities were as follows:

systemic blood hypertension (5/9), type 2 diabetes (2/9), COPD (2/9), coronary artery disease (1/9), atrial fibrillation (1/9), hypertrophic cardiomyopathy (1/9), as reported in Table 1. All patient underwent high

resolution chest computed tomography at baseline that showed a progressive stage of disease, with diffuse bilateral subpleural groundglass opacities.

Other common findings were consolidations and traction bronchiolectasis. All patients experienced a radiological improvement during ICU stay. Base

line PaO₂/FiO₂ was 109 ± 45 mm Hg. After a long course of ventilation all patient improved until a sta

ble mean ventilation PaO₂/FiO₂ of 336 ± 72 mm Hg.

Right after initiation of HFNC (2 hours), PaO₂/FiO₂ was 254 ± 69.3 mm Hg (Figure 1). No signs of respi

ratory distress were observed; in fact, the respiratory rate was stable and ranged between 18 and 22 on HFNC (vs. 20–24 on ventilation). Mean ROX index at two hours was 11.17 (range: 7.38–14.4). It was con

sistent with low risk of HFNC failure. No difference was observed on lactate when patients switched to HFNC (1.72 ± 0.77 vs. 1.27 ± 0.46 mmol L¹; P = NS).

After 48 hours of HFNC oxygen therapy (day 3), PaO₂/FiO₂ significantly increased compared to day 1, with a mean of 396 ± 83.5 mm Hg (± 142 mm Hg;

P < 0.0001). All patients recovered from respiratory failure at rest (PaO₂ > 60 mm Hg in room air) after 7 ± 4.1 days. Patients outcomes are reported in Table 1.

During the HFNC period it was possible to per

form a relevant rehabilitation plan. Initially all pa

tients received respiratory physiotherapy and mo

bilisation, followed by active physiotherapy.

DISCUSSION

Soon after initiation of HFNC (2 hours) the mean PaO₂/FiO₂ was lower than previous ventilation val

ues. Having a constant FiO₂, this was probably caused by the lower PEEP delivered in HFNC [13].

The maximum PEEP during HFNC is estimated at about 5 cm H₂O, while the mean PEEP applied dur

ing ventilation was 10 cm H₂O [14]. All patients were stable and showed no signs of distress or intoler

ance. In fact, respiratory rate and lactate were stable when patients switched to HFNC. ROX index was consistent with low risk of HFNC failure, suggesting its reliability could be extended to COVID19.

As per our experience, HFNC was deemed effi

cient after 48 hours of therapy. Efficacy was deter

mined as a combination of a continuous upward trend of PaO₂/FiO₂ (Figure 1) with a good tolerance.

Indeed, on day 3 the PaO₂/FiO₂ increased to a mean

of 396 mm Hg. Thereby, it exceeded the average level during ventilation.

After this stabilisation step, we progressively decreased FiO₂ day by day according to blood gas values [15]. All patients recovered from respiratory failure at rest (PaO₂ > 60 mm Hg in room air) after 7 ± 4.1 days.

Afterwards all patients continued to receive heated humidified HFNC without oxygen enrich

ment (FiO₂ 21%) at rest to reduce their work of breathing [16]. We report that HFNC also made it easier to perform a relevant rehabilitation plan with respiratory physiotherapy and mobilisation.

CONCLUSIONS

In severe COVID19 respiratory failure, HFNC is a valid option to support oxygenation in the post

ventilation period. Effectiveness and comfort should be assessed between 2 and 48 hours. Clinical out

comes, oxygenation, and ROX index should be con

sidered to rule out the need for intubation. Further evidence is required for firm conclusions.

ACKNOWLEDGEMENTS

1. Financial support and sponsorship: none.

2. Conflicts of interest: none.

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FIGURE 1. Daily variation of PaO₂/FiO₂ on high-flow nasal cannula

PaO₂/FiO₂

600 500 400 300 200 100

0

Days

1 2 3

Patient 1 Patient 6

Patient 2 Patient 7

Patient 3 Patient 8

Patient 4 Patient 9

Patient 5

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